I've been a big fan of MOI for quite some time now and have finally taken the plunge.
I was looking for a little advice on how to create the shape in the images below.

If this was modo, I'd just Sub-D the piece. And I have, but I wanted to re-create it using MOI.
I think that the Loft or the Network tool would be the right choice, just not sure how to use them this piece.

Hi Scott - just a quick note about your attached file - that's not going to work with Network because the curves don't form a regular grid pattern - it almost does but not quite.

The top side is set up ok for network, with this one curve here:

But then instead of having curve set out for the left, right, and bottom areas of the network you've instead just got one single long curve running all the way through here:

That long curve that's wrapping around and touching both horizontal as well as vertical lines of the network means that it does not "unwrap" into a 2D pattern and so that curve arrangement won't work for Network.

Basically Network requires that the curves have a way to unwrap to a 2D grid, similar to the way that a flat rectangular map of the world is unwrapped from a 3D globe, where you have 2 sets of lines, one for longitude and one for latitude and although they can cross over each other it does not work to have lines of longitude and/or latitude having an endpoint all on one single curve like you have here.

Hi Scott, so one thing to keep in mind is that more amorphous blobby-ish types of shapes are not very well defined only by 2D profile curves and using a lot of 2D curves tends to be the primary type of modeling that NURBS is the most useful and strongest in.

So it's not like you would really see a great advantage in doing this style of model in MoI rather than in sub-d in Modo, it's probably more in the area of stuff where you would want to be doing in sub-d instead.

For models that have a stronger 2D element to them, that's where NURBS modeling will really shine the most as an alternate modeling toolset to sub-d since you can then use 2D drawn curves to construct large chunks of your model really quickly and accurately.

So the very nature of the model that you're targeting here is not really going to show you the main benefits of NURBS modeling, that's something to just generally keep in mind. Instead of working at the sort of "highest convenience level" you'll instead be working in more low level and advanced types of tools right from the get-go.

Anyway, though, for doing stuff like this in NURBS it ends to be better to not try to do too much all at once in one single surfacing operation, especially if there is a major transition in shape happening.

Instead you want to look for the transitions between major forms, and focus instead of building those major forms separately and then they get connected together either with fillets or blends.

To look for transition areas, look for places of the model that have a kind of tighter bend in them, like in your case see these areas here:

Those are transition zones making a connection between different broader forms. The broader forms would be these pieces here:

So generally you would want to try to model those broader form pieces individually (it's ok and even desirable to let them just stick through each other while constructing them), then they either get combined together into a single solid and have a fillet put in between them, or you cut back some empty space in between them and use the Blend command.

EDIT: and Burr above shows a good example of the kind of model that you would shoot for - notice there how he's built the larger forms as separate pieces initially like I describe above here.

In general surfacing stuff does not tend to work very well if you try to force too complex of a form that goes through a lot of different shapes to be the result of one single surfacing operation, basically with too many shapes trying to all apply pressure onto a single surface it will tend to over constrain things and make for ripples and lumps and things like that.

When you're doing surface construction you want to build a surface for each broad shape in the result instead, then transitions are added separately after that.

Another thing that can help is that you often times don't want to try to construct things to some irregular outline initially, instead make a broad shape that continues through the outline and then use a boolean or trimming operation to slice off the broad shape. A lot of times people with a polygon modeling background have difficulty with thinking about building extended parts like that.

Also see here for some links to previous discussions about that "build extended pieces and then cut them up" type technique, and also some links to discussions oriented towards helping polygon modelers get a bit more used to NURBS modeling techniques:

Hi Scott - making shapes in a separate "patch by patch" method like that will tend to naturally result in shapes that have creases where they meet up. That happens because your shapes basically stop abruptly at their ending spot.

Usually to get smooth surfaces you need to instead build things in large broader pieces rather than as doing them as separate pieces.

See here for some more explanation of how building a shape that "stops" at a boundary will result in creases:

Notice how in Burr's previous example above, the 2 separate forms for each broad shape is not made up of fragmented bits but instead one big single surface?

> even after running the Join command.

There is a major difference from how Joining works in NURBS modeling as compared to polygon modeling.

In NURBS modeling joining makes a connection between pieces but it's purely a topological connection where the system now knows how the outer skin of a solid is connected together - nothing changes in the actual geometric shape of surfaces when they are joined.

Also in a polygon modeler even if you are not doing sub-d smoothing you can merge polygons together and then they get the sort of fake smooth phong/gouraud shading applied to them to make the rendered result look like it's smooth even though it's really made up of flat polygons. That's also very different from NURBS modeling - NURBS modeling doesn't use any kind of fake shading to it at all, things will only be smooth if the surfaces that you have constructed actually are smooth to one another.

Basically with NURBS modeling you don't really want to be building things in a patch-by-patch manner like that - instead for things that are supposed to be smooth build them out of a larger single surface, and when there is a transition between broad shaped forms, don't try to build that transition directly into your surfaces, instead focus on building each broad form separately and then they will get trimmed or booleaned where they cut each other and have a transition constructed using fillet or blend.

Blend creates a new surface in the empty space between some edge curves. In your case you've got all the pieces touching with no empty space between them, so there's no room available for a blend surface to be created, that's why it would not do anything for you.

Booleans only intersect objects with one another to cut away parts. Similar to Join, Booleans will not alter the geometric shape of a surface, they will only alter trimming boundaries to cut away some more areas of surfaces.

Like I mentioned previously, really this kind of project with semi-organic type forms does not tend to leverage the best strengths of NURBS modeling - if you're already comfortable doing sub-d modeling then doing things that are more sculptured in shape and semi-blobby-ish without much 2D profiles to them will tend to be better done in your sub-d modeling program.

Models that have more 2D design elements from them and things like holes and cut away areas will be the kind of stuff where NURBS modeling becomes much more useful for you probably. The particular model that you've targeted here is not in that kind of category though.

In the video, I talked about a poor decision in my model to create a "radiused curve" in the originating curve, instead of a hard edge.. This can create problems later.

I tried to make note of showing how the red curves from your original model are trying to mimic what the fillet creates. Trying to hand model those would be hard. I suppose the trick is to figure out what the original shapes and orientations are that would have the fillet edges match a "picture" or somthing...

I also think that if you are trying to "totally match" from a picture, you may get better results by using a revolove, instead of the blend i use, on the initial pod shape.. Revolving half of that curve, then turning on control points will allow you to change the shape in a way to match your base curves you started with...